Research On Key Technologies Of Software Defined Constellation Communication System

Software Definition Network(SDN)separates the control plane and forwarding plane of the network,realizing a centralized,open,and standardized network control plane.Under the network architecture for a software-defined constellation communication system,the network can be flexibly managed,controlled,and defined through the software configuration on the control plane,and the following problems can be solved:low payload of satellite nodes in the constellation communication system,dynamic inter-satellite links,frequent changes in network topology,weak Quality of service(QoS)guarantee capability,and difficult network adjustment and upgrading.At present,there are few technological studies on software-defined constellation communication systems,and some studies only stay in the architectural design phase.Especially,studies in key technologies such as routing algorithms,QoS guarantee system,and resource management policies for software-defined constellation communication systems are less..This dissertation conducts an in-depth study of the architecture,capacity characteristics,and key technologies of software-defined constellation communication systems.Its main innovations include the following:(1)Proposes the network structure,functional modules and Policy Control and Charging(PCC)system architecture of the SDN constellation communication system,solves the problems such as poor on-satellite payload capacity,weak service control capability,closed system structure,difficult upgrade or reconstruction,and unsystematic service QoS guarantee.At present,most studies on satellite constellation use a distributed system,and integrate the control plane and service plane.Satellite nodes need link maintenance,status monitoring,routing calculation and other network control functions,thus consuming precious on-satellite payload and inter-satellite link resources.This dissertation uses a network structure with separated control plane and forwarding plane and applies SDN technology into the constellation communication system.The network control is centrally deployed on the SDN controller to maximally simplify the functional structure of the satellite nodes.In addition,this dissertation also designs a network architecture,functional modules,and system functions based on SDN constellation system,supporting and providing guidance for subsequent studies on key technologies of SDN constellation communication systems.In this dissertation,the PCC architecture is introduced into the SDN constellation communication system,and the northbound Application Programming Interface(API)interface of the SDN controller is connected to the PCC system,thus the routing protocol and the Policy and Charging Rules Function(PCRF)policy can be called mutually.The type and service level of the service initiated by the satellite terminal user are matched,thus achieving policy control at the service forwarding level and classified guarantee for the user Service Level Agreement(SLA)and service QOS.(2)A SDN-Based Multi-Path Routing(SMPR)algorithm is proposed to solve the problems such as weak load balancing ability,few routing factors,poor adaptability to topology changes,and so on of the constellation communication system.Currently,due to the limited payload of the satellite node,it is difficult for the routing algorithm of constellation communication system to have overall consideration of the network end-to-end transmission latency,data packet loss rate,network load balancing,inter-satellite link switchover,and other global factors,and the common problems are that the service QoS service support ability is weak,traffic balancing is poor etc..This dissertation proposes centralized deployment of the SMPR routing algorithm in the SDN controller,which uses 3 indicators-latency of inter-satellite link,residual bandwidth and bit error rate to define the initial weighting function of the link,then considers the link stability function and criticality function defined by inter-satellite link switchover and usage frequency,determines the Label Switching Path(LSP)link selection probability function based on the above 3 indicators,realizes the dynamic routing of service on multiple LSP links from source to the destination,so that the selection of packet routing considers latency,residual bandwidth,bit error rate,link switchover,load and other parameters,balances the network traffic,improves network utilization,and reduces the packet loss rate and latency jitters caused by link switchover.This is how the whole performance of the constellation communication system can be enhanced and traffic engineering in the constellation system can be implemented dynamically according to the traffic variations.(3)A cross-layer resource allocation algorithm of the SDN-based constellation communication system is proposed to solve the problem that the constellation communication system lacks the ability to allocate physical layer channel resources according to the demand of QoS,the whole network resource status,user channel quality,and other comprehensive factors.At present,the cross layer resource allocation algorithm of satellite communication systems is mainly based on the demand of QoS guarantee and allocates physical layers with different working modes by Adoptive Code Modulation(ACM)technology so that improving the utilization rate of resources and meeting the security demand of QoS service can be balanced.Due to the lack of centralized control,analysis and calculation of whole network service applications,network resources,channel quality of the constellation communication system,most studies on cross-layer resource allocation of satellite communication systems are still confined to resource allocation algorithm study for a specific issue which lacks the abilities of comprehensive resource allocation and QoS guarantee for various network states and different types of services.The SDN-based constellation communication system in this dissertation adopts the mode of centralized setting at the control layer,boasts the ability of whole-network state information perspective and resource virtualization.Efficient cross-layer packet allocation algorithms can be directly deployed on the SDN controller according to the status of network operation,and various resources of the constellation communication system can be virtualized through Network Function Virtualization(NFV),implementing centralized allocation scheduling according to the needs of users and services.Through overall consideration of the application layer services and the physical layer channel resources as well as the characteristics of satellite network structure and channel quality,balance of service QoS and resource utilization efficiency is achieved.In addition,in order to better evaluate the quality of users' channels,this dissertation also proposes the estimation model for the main interference band of the rain attenuation and studies the evaluation algorithm of satellite ground link quality for users.